/Engine/Source/Runtime/Core/Public/Misc/MapErrors.h
BSP Brush {Brush Actor} : Brush has zero polygons - please delete!: This warning indicates that you have a brush in the level that doesn't have any polygons associated with it. The brush should be deleted as it isn't doing anything useful.
static [FLazyName](API\Runtime\Core\UObject\FLazyName) BrushZeroPolygons;